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In supplying a high volume flow of oxygen-enriched air from a molecular
sieve type gas separation system, two sets of molecular sieve beds
are coupled in parallel. The beds and of each bed set are cyclically
subjected to a charge/adsorption on-stream phase followed by a purge/desorption
regeneration phase and are controlled to operate in overlapping
sequence with respect to each other. At the same time the corresponding
beds are controlled to operate in antiphase relationship to each
other.
A gas flow controller 10 for use with a molecular sieve type oxygen
enrichment of air system 5 delivering oxygen enriched air for breathing
by aircrew ensures that a constant preset quantity of product gas
in the form of oxygen enriched air flows from the system 5 so that
it performs under varying demand conditions and varying air supply
conditions to maintain desired levels of oxygen concentration in
the oxygen enriched air delivered to the aircrew by means of a demand
regulator 6 and a breathing mask 7. A servo-operated valve means
20 bleeds air from downstream of a venturi section 15 provided between
in the inlet 13 and outlet 14 of a gas flow duct 12 in the body
11 of the controller 10. The servo-operated valve means 20 is regulated
by an actuator means 29 responsive to pressure difference through
the venturi section 15. An adjustment means 42 responsive to duct
pressure upstream of the venturi section and either to varying cabin
absolute pressure or to varying cabin differential pressure, applies
a biasing force to the actuator means.
An attrition resistant molecular sieve composition comprising a
generally spherical, high porosity molecular sieve particle having
an exposed surface coated with a thin, generally uniform layer of
solid lubricant which can be employed in fixed, moving or fluidized
beds with low attrition and without significantly reduced activity.
A monitoring system for determining the concentration of oxygen
in the product gas of an oxygen enriching system comprises a plurality
of pneumatic nor gates. Means are provided for coupling the outlet
port of each gate to the control port of the subsequent gate to
form a closed loop and a plurality of molecular sieve beds are pneumatically
connected one each to the control port of the nor gates. The molecular
sieve beds adsorb oxygen from the product gas to attenuate the rate
of pressure change in the control ports and thus, the oscillation
frequency of the monitor. The oxygen concentration of the product
gas may be inferred from the oscillation frequency of the monitor.
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